1. Field of the Invention
This invention relates to hydrogels, and, more particularly, to stable, aqueous, crosslinked cationic hydrogels which are effective viscosity modifiers and swelling agents, and can function as conditioners in anionic surfactant-containing shampoo formulations.
2. Description of the Prior Art
Polymeric crosslinked polyacrylic acid thickeners have been used to modify the physical form, function and aesthetics of personal care formulations. However, such anionic hydrogels do not maintain their thickener action at a low pH; also they are not compatible in a cationic formulation.
Similarly, Aizawa, T. et al, in U.S. Pat. No. 5,338,815, described the preparation of fine particulate crosslinked N-vinylamide homo- and co-polymers, particularly poly-N-vinylformamide and poly-N-vinylacetamide, which had thickening properties; however, only in neutral water, (pH 6-8).
Other references of interest in this art are U.S. Pat. Nos. 5,321,110; 5,603,926; 5,663,258 and 5,684,105; Y. Zhong and P. Wolf, Hydrogel Prepared from Crosslinked Vinyl Pyrrolidone and Vinyl Acetate Copolymer, Polymer Reprints 1997,38 (2), p. 578; and Y. Zhong and P. Wolf, Swelling Properties of Crosslinked Vinylpyrrolidone Homopolymers and Vinylpyrrolidone/Vinyl Acetate Copolymers, Polymer Reprints 1998,39 (2), p. 461.
Accordingly, it is desired to provide a stable, aqueous crosslinked (XL) cationic hydrogel which is an effective viscosity modifier, and capable of adsorbing large amounts of water per weight of polymer, which is advantageous for hair thickening, conditioning and styling, in formulations having an anionic surfactant, across a wide pH range including low pHs.
These and other objects and features of the invention will be made apparent from the following description thereof.